Most all PVR's encrypt the video files so that they can't be watched on other devices. The ones that do let you copy the files to PC is for archiving only. You need to copy them back to the PVR in order to watch them.
Also, you didn't mention which PVR you have. On a tivo, simply put the tivo's IP address in your browser. The user name is tivo and the password is your tivo's media access key which can be found in the tivo menus.